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April 14, 2014

by Chris Mann

The clocks went forward at the end of March and the Earth is motoring along its orbit such that between mid March and mid May, the real night (minus astronomical twilight) will have nearly halved from 9 hours to just over 5½ hours. Disaster! What’s more all those beautiful winter constellations are fast disappearing in the lengthening evening twilight.

So for those few able to get out late for a few hours, this is for you:

Well thank goodness for Mars. At opposition on 8 April and at its closest approach to Earth on 14 April and visible all night long in Virgo. At mag -1.4, pretty bright.

We’ve also got the wonderful area east of Leo: Coma Berenices and northern Virgo. We just need a dark sky!

Not to forget Saturn. Rising now well before midnight, it in opposition on May 10, moving retrograde in Libra. At nearly an angle of nearly 24 degrees, the rings are well presented.

There were two pieces of research which caught my eye this month and I think are of great interest. One concerns the development of our solar system and the other gravitational waves. Details can be found in the presentation below:

Of course, I can’t go without mentioning a variable star. Since Ursa Major dominates the sky at present, I’ve chosen T Uma, a Mira-type variable. Mira variables are red giant stars in the very late stages of stellar evolution. They are characterised by very red colours, variation periods longer than 100 days, and amplitudes greater than 2.5 magnitudes at visual wavelengths. They also pulsate, which produces a change in temperature along with radius, both of which factors cause the variation in luminosity. T Uma varies between around 8th magnitude to around 13th magnitude every 8½ months (257 days).